520w rms 4ohms to 8ohms rms conversion

[jonpaulmusic]

Hi guys and girls just a quick question as I cant find the answer elsewhere.

I've just bought an alto tmx200dfx which has two class d amps and it shows the following spec's

Power Consumption Stereo mode
2 x 500W @ 4 Ohm (EIAJ) 2 x 340 W @ 4 Ohm (RMS)
2 x 750W @ 4 Ohm (EIAJ) 2 x 520 W @ 4 Ohm (RMS)

Bridge mode
1000 W @ 8 Ohm (EIAJ)
1500 W @ 8 Ohm (EIAJ)

Firstly does anyone know what the bits highlighted in red would convert to for 8 ohm cabs in rms please?

Secondly I have 2 x impulse 1015's at 8ohms which is 500w rms black widow 1000w program and 2000w peak if I was to run 2 of these in parallel on one side of the bigger amp (bringing this down to 4 ohms) and two on the otherside of the bigger amp (bringing this down to 4 ohms) does this mean I am then running 1000w rms on each side of the bigger amp but with a power output of only 520w rms @ 4 ohms from the amp what effect will this have on my cabs and or sound or is this the safest way to run the amp as then it should be impossible to blow the cabs?

Hope all that made sense and look forward to your thought on this

 

[richie00boy]

For an ideal amplifier the 8 ohm powers would be halved compared to the 4 ohm powers, but it depends on how much the power supply sags.

As to your second question, two 8 ohm speakers of 500W each onto an amp would be a load of 4 ohms that can take 1000W.

Contrary to popular belief, an amp having lower power rating than the speaker is just as likely to blow a speaker than a one with higher power. The low power amp fries the voice coils, the high power amp tends to over-excurt but can also fry voice coils.

I would look at using one speaker per side and the amount of box volume that the second speaker would have taken, give that to the single speaker.

 

[KatieandDad]

I wonder what the EIAJ means. Is it just flannelling to make the figures look bigger for the boy racers ? The only real figures that have any meaning are the True RMS figures.

When considering true RMS you need to know several things.

Generally - not always:-

As you increase the speaker impedance you can sometimes increase the power rails.

If you increase the heatsinking the amps might be able to work harder.

So, for ABSOLUTE MAX RMS power the simple equation of 8 Ohms gives 1/2 the power of 4 Ohms might not necessarily be true.

Anyone wanting to work the amps at their max is just asking for early failure though.

 

[mr. doom]

I wonder what the EIAJ means. Is it just flannelling to make the figures look bigger for the boy racers ? The only real figures that have any meaning are the True RMS figures.

When considering true RMS you need to know several things.

Generally - not always:-

As you increase the speaker impedance you can sometimes increase the power rails.

If you increase the heatsinking the amps might be able to work harder.

So, for ABSOLUTE MAX RMS power the simple equation of 8 Ohms gives 1/2 the power of 4 Ohms might not necessarily be true.



Anyone wanting to work the amps at their max is just asking for early failure though.

This and the 3db you gain by doubling power is barely noticeable in the real world.